View Compilation Error

0_0_18161835_22944.cpp: In function 'int main()':
0_0_18161835_22944.cpp:23:15: error: 'mod' was not declared in this scope
    ll b=(c-c1+mod)%mod;
               ^
0_0_18161835_22944.cpp:24:17: error: 'powm' was not declared in this scope
    if (powm(b,k2)==c2){
                 ^